Smith, E. G., Janzen, H. H. and Kröbel, R. 2015. Yield and profitability of fallow and fertilizer inputs in long-term wheat rotation plots at Lethbridge, Alberta. Can. J. Plant Sci. 95: 579-587. A long-term, 42-yr study was used to determine the impacts of crop rotation and fertility management on wheat yield and profitability. Crop rotations included continuous wheat (W), fallow-wheat (FW), and fallow-wheat-wheat (FWW). Original plots were split for nitrogen (N) and phosphorus (P) fertility treatments, a two-factor factorial for N (0 and 45 kg ha^-1) and P (0 and 20 kg ha^-1). Phosphorus increased yield during the first half of the period, but had little impact during the last half. Nitrogen had no yield impact on fallow crops during the first half of the period, but had a positive impact during the last half, and throughout for wheat after wheat. The soil became incapable of releasing adequate N for wheat after fallow. Simulated distributions of net returns determined the W rotation with N and P fertilizer had, on average, the highest but also the most variable net return. Net return was higher during the last half of the study, and the fertilized continuous wheat rotation had the highest average net return. The continuous wheat rotation was more risky, and producers averse to risk would prefer the less risky fertilized fallow-wheat rotation.